2229 - Stereotactic Body Radiation Therapy for the Treatment of Spinal Chordomas - A Single Institutional Retrospective Review
Presenter(s)
G. I. Song1, E. E. Obi2, J. C. Bastick III2, T. Hattery1, S. T. Chao3, E. H. Balagamwala4, L. Angelov3, E. S. Murphy3, S. R. Campbell4, and P. Pendyala5; 1Cleveland Clinic Foundation, Cleveland, OH, 2Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic Foundation, Cleveland, OH, 3Rose Ella Burkhardt Brain Tumor & Neuro-Oncology Center, Cleveland Clinic Foundation, Cleveland, OH, 4Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, 5Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH
Purpose/Objective(s): Chordomas of the spine are rare, locally aggressive bone tumors arising from notochordal remnants with high local recurrence rates despite multimodality management. The standard of care consists of maximal safe surgical resection followed by radiation therapy. Stereotactic body radiation therapy (SBRT) enables delivery of ablative doses with steep dose gradients, potentially optimizing local control (LC) while minimizing spinal cord toxicity. We evaluated institutional outcomes to characterize the efficacy, failure patterns, and toxicity profile of SBRT for spinal chordomas.
Materials/Methods: This retrospective review includes patients with histologically confirmed spinal chordomas treated with SBRT at a single institution from 2016-2025. Outcomes were analyzed per treated lesion. Primary endpoints were LC and distant control (DC). Local failure was classified as in-field (=80% recurrence volume within the 95% prescription isodose line), marginal (20-80%), and out-of-field (<20%). Secondary endpoints included pain relief and toxicity. Time-to-event outcomes were estimated using the Kaplan-Meier method.
Results: Nine patients with spinal chordoma received SBRT to 19 sites for radiation naive (n=11) or previously irradiated disease (n=8). The median age was 63 (range 51-86). Ten lesions were treated with definitive SBRT, and nine were treated with adjuvant SBRT. Tumor locations spanned the cervical (n=2), thoracic (n=1), lumbar (n=12), and sacral/coccygeal (n=4) spine. SBRT regimens included 16 Gy / 1 fx (n=3), 30 Gy / 3 fx (n=14), and 30 Gy / 4 fx (n=2). Median planning target volume was 125.82 cc (range 14.4-396.7). At a median follow up of 39 months, estimated 3-year LC and DC were 51.8% and 57.1% respectively. When evaluated by subset, 3-year median local control (41.2 months vs 25.8 months) favored the radiation naive compared to re-irradiation group. Local failure patterns were 40% marginal (n=4), 30% in-field (n=3), 30% out-of-field (n=3). Among sites with evaluable pain data (n=13), 77% (n=10) achieved partial pain relief with a median duration of 4 months. Toxicities included pain flare (n=5, 26%), vertebral compression fracture (n=4, 21%), myelopathy (n=1, 5%), and plexopathy (n=3, 16%).
Conclusion: SBRT for spinal chordoma yields moderate local control with an estimated 3-year local control rate of 51.8%, with marginal failures representing the predominant pattern. Our data also showed trends of worse LC associated with the re-irradiated subgroup, possibly indicating more radioresistant disease following RT. SBRT provided meaningful symptomatic palliation with an acceptable though notable toxicity profile. These findings support SBRT as a component of multimodal management for newly diagnosed and recurrent spinal chordomas, particularly for recurrent or surgically inaccessible disease.